Midterm

Just a reminder that the midterm exam will be held on Monday, November 7th. It's worth 20% of your overall grade.

There are a variety of questions on the midterm:  different types of argument evaluation, some short answers, a mini-essay, and extra credit. It covers everything we've gone over in class so far:

• Philosophy
  -Definitions
  -Doing philosophy
• Arguments
  -Evaluation: truth and support tests
  -Types: arguments from example, arguments by analogy, causal arguments, arguments from authority, deductive arguments
  
• Knowledge
  -Definition: Plato says true belief doesn't equal knowledge
  -Skepticism
  -Descartes: uncertain of childhood beliefs, senses, and reasoning; certain he's thinking and he exists
• God Stuff
  -Cosmological Argument: Aquinas's uncaused 1st cause version
  -Ontological Argument: Anselm's version, Guanilo's criticism
  -Design Argument: arg by analogy version, inductive version, Hume's criticisms of the analogy & inductive versions, abductive version

An Argument's Support

One of the trickier concepts to understand in this course is the structure (or support) of an argument. This is a more detailed explanation of the term. If you've been struggling to understand this term, the following might help you.

An argument's structure is its underlying logic; the way the premises and conclusion logically relate to one another. The structure of an argument is entirely separate from the actual meaning of the premises. For instance, the following three arguments, even though they're talking about different things, have the exact same structure:

1) All tigers have stripes.
Tony is a tiger.
Tony has stripes.

2) All humans have wings.
Sean is a human.
Sean has wings.

3) All blurgles have glorps.
Xerxon is a blurgle.
Xerxon has glorps.

There are, of course, other, non-structural differences in these three arguments. For instance, the tiger argument is overall good, since it has a good structure AND true premises. The human/wings argument is overall bad, since it has a false premise. And the blurgles argument is just crazy, since it uses made up words. Still, all three arguments have the same underlying structure (a good structure):

All A's have B's.
x is an A.
x has B's.

Evaluating the structure of an argument is tricky. Here's the main idea regarding what counts as a good structure: the premises provide us with enough information for us to figure out the conclusion from them. In other words, the premises, if they were true, would logically show us that the conclusion is true. So, if you believed the premises, they would convince you that the conclusion is worth believing, too.

Note I did NOT say that the premises are actually true in a good-structured argument. Structure is only about truth-preservation, not about whether the premises are actually true or false. What's "truth preservation" mean? Well, truth-preserving arguments are those whose structures are such that if you stick in true premises, you get a true conclusion.

The premises you've actually stuck into this particular structure could be good (true) or bad (false). That's what makes evaluating an arg's structure so weird. To check the structure, you have to ignore what you actually know about the premises being true or false.

Good Structured Arguments (Valid)
If we assume that all the premises are true, then the conclusion will also be true for an argument to have a good structure. Notice we are only assuming truth, not guaranteeing it. Again, this makes sense, because we’re truth-preservers: if the premises are true, the conclusion that follows will be true.

EXAMPLES:
1) All humans are mammals.
All mammals have hair.
All humans have hair.

2) If it snows, then it’s below 32 degrees.
It is snowing right now.
It’s below 32 degrees right now.

3) All humans are mammals.
All mammals have wings.All humans have wings.

4) Either Yao is tall or Spud is tall.
Yao is not tall.
Therefore, Spud is tall.

Even though arguments 3 and 4 are ultimately bad, they still have good structure (their underlying form is good). The second premise of argument 3 is false—not all mammals have wings—but it has the same exact structure of argument 1—a good structure. Same with argument 4: the second premise is false (Yao Ming is about 7 feet tall), but the structure is good (it’s either this or that; it’s not this; therefore, it’s that).

To evaluate the structure, then, assume that all the premises are true. Imagine a world in which all the premises are true. In that world, are you able to figure out from the premises that the conclusion is also true? Or can you imagine a scenario in that world in which the premises are true, but the conclusion is still false? If you can imagine this situation, then the argument's structure is bad. If you cannot, then the argument is truth-preserving (inputting truths gives you a true output), and thus the structure is good.

Bad Structured Arguments (Invalid)
In an argument with a bad structure, you can’t draw the conclusion from the premises – the premises don’t give you enough information. Bad structured arguments do not preserve truth.

EXAMPLES:
1) All humans are mammals.
All whales are mammals.
All humans are whales.

2) If it snows, then it’s below 32 degrees.
It doesn’t snow.
It’s not below 32 degrees.

3) All humans are mammals.
All students in our class are mammals.
All students in our class are humans.

4) Either Yao is tall or Spud is short.
Yao is tall.
Spud is short.

Even though arguments 3 and 4 have all true premises and a true conclusion, they are still have a bad structure, because their form is bad. Argument 3 has the same exact structure as argument 1—a bad structure (it doesn’t preserve truth).

Even though in the real world the premises and conclusion of argument 3 are true, we can imagine a world in which all the premises of argument 3 are true, yet the conclusion is false. For instance, imagine that our school starts letting dogs take classes. The second premise would still be true, but the conclusion would then be false.

The same goes for argument 4: even though Spud is short (Spud Webb is around 5 feet tall), this argument doesn’t guarantee this. The structure is bad (it’s either this or that; it’s this; therefore, it’s that, too.). We can imagine a world in which Yao is tall, the first premise is true, and yet Spud is tall, too.

Evaluating Deductive Arguments

Here are the answers to the handout on evaluating deductive arguments that we did as group work in class.

1) All bats are mammals.
All mamammals live on earth.
All bats live on earth.

P1- true
P2- true
support- valid
overall- sound

2) All email forwards are annoying.
Some email forwards are false.
Some annoying things are false.

P1- questionable ("annoying" is subjective)
P2- true
structure- valid (the premises establish that some email forwards are both annoying and false; so some annoying things [those forwards] are false)
overall- unsound (bad first premise)

3) All males in this class are humans.
All females in this class are humans.
All males in this class are females.

P1- true
P2- true
support- invalid (the premises only tell us that males and females both belong to the humans group; we don't know enough about the relationship between males and females from this)
overall- unsound (bad support)

4) No humans are amphibians.
All frogs are amphibians.
No frogs are humans.

P1- true
P2- true
structure-  valid (the premises say that frogs belong to a group that humans can't belong to, so it follows that no frogs are humans)
overall- sound

5) All bats are mammals.
All bats have wings.
All mammals have wings.

P1- true
P2- true (if interpreted to mean "All bats are the sorts of creatures who have wings.") or false (if interpreted to mean "Each and every living bat has wings," since some bats are born without wings)
support- invalid  (we don't know anything about the relationship between mammals and winged creatures just from the fact that bats belong to each group)
overall- unsound (bad support)

6) Some dads have beards.
All bearded people are mean.
Some dads are mean.

P1- true
P2- questionable ("mean" is subjective)
support- valid (if all the people with beards were mean, then the dads with beards would be mean, so some dads would be mean)
overall- unsound (bad 2nd premise)

7) Oprah Winfrey is a person.
Some people ate tacos yesterday.
Oprah Winfrey ate tacos yesterday.

P1- true
P2- true (you might not have directly seen anyone eat tacos, but you have a lot of indirect evidence... with all the Taco Bells, Don Pablos, etc., surely lots of people ate tacos yesterday)
support- invalid (the 2nd premise only says some ate tacos; Oprah could be one of the  people who didn't)
overall- unsound (bad support)

8) All students in here are mammals.
All humans are mammals.
All students in here are humans.

P1- true
P2- true
structure- invalid (the premises only tell us that students and humans both belong to the mammals group; we don't know enough about the relationship between students and humans from this; for instance, what if a dog were a student in our class?)
overall- unsound (bad structure)

9) All hornets are wasps.
All wasps are insects.
All insects are scary.
All hornets are scary.

P1- true!
P2- true
P3- questionable ("scary" is subjective)
structure- valid (same structure as in argument #1, just with an extra premise)
overall- unsound (bad 3rd premise)

10) If Sean sings, then students cringe.
Sean is singing right now.
Students are cringing right now.

P1- questionable (since you haven't heard me sing, you don't know whether it's true or false)
P2- false
structure- valid
overall- unsound (bad premises)

11) If Sean sings, then students cringe.
Sean isn't singing right now.
Students aren't cringing right now.

P1- questionable (again, you don't know)
P2- true
structure- invalid (from premise 1, we only know what happens when Sean is singing, not when he isn't singing; students could cringe for a different reason)
overall- unsound (bad 1st premise and structure)

12) All students in here are humans.
Most humans are shorter than 7 feet tall.
Most students in here are shorter than 7 feet tall. 

P1- true
P2- true!
support- invalid (the premises state a strong statistical generalization over a large population, and the conclusion claims that this generalization holds for a much smaller portion of that population; even though it's likely that most students in here are, in fact, shorter than 7 feet tall, it nevertheless could be true that the humans in here are a statistical anomaly)
overall- unsound (bad support)

13) (from Stephen Colbert)
Bush was either a great prez or the greatest prez.
Bush wasn’t the greatest prez.
Bush was a great prez.

P1- questionable ("great" is subjective)
P2- questionable ("great" is subjective)
support- valid (it's either A or B; it's not A; so it's B)
overall- unsound (bad premises)

14) If Sean sings, then students cringe.
Students are cringing right now.
Sean is singing right now.

P1- questionable (again, you don't know)
P2- false
structure- invalid (from premise 1, we only know that Sean singing is one way to guarantee that students cringe; just because they're cringing doesn't mean Sean's the one who caused it; again, students could cringe for a different reason)
overall- unsound (bad premises and structure)

15) If Sean sings, then students cringe.
Students aren't cringing right now.
Sean isn't singing right now. 

P1- questionable (again, you don't know)
P2- true
structure- valid 
overall- unsound (bad 1st premise)

16) If there is no God, then life is meaningless.
Life isn't meaningless.
There is a God.

P1- questionable (that's not an obvious claim to prove or disprove)
P2- questionable (again, that's not an obvious claim to prove or disprove)
support- valid (the same structure as argument #15)
overall- unsound (bad premises)

An Expert for Every Cause

Looking for links on arguments from authority? This is your post! First, here's an interesting article on a great question: How are those of us who aren't experts supposed to figure out the truth about stuff that requires expertise?

Not all alleged experts are actual experts. Here's a method to tell which experts are phonies (this article was originally published in the Chronicle of Higher Education).

We should judge experts who are into making predictions on how accurate their predictions turn out.  Well, most experts are really bad at predicting, and have the same biases as non-experts.

It's important to check whether the person making an appeal to authority really knows who the authority is. That's why we should beware of claims that begin with "Studies show..."

And here's a Saturday Night Live sketch in which Christopher Walken completely flunks the competence test.

Non-Deductive Arguments

Here are the answers to the group work we did in class on args by example, args by analogy, args from authority, and args about causes. Conclusions are in bold.

1. That Honus Wagner baseball card shouldn’t be that valuable. After all, it’s made out of cardboard, and cardboard boxes at Pathmark are super cheap.

Analogy
Bad - Material isn't always a relevant similarity to draw a conclusion about value: baseball cards are typically valued for their rarity, not what they're made of.

2. China, India, Brazil, Nigeria, and Russia are all countries with populations greater than 100 million citizens. Hence, most countries have populations larger than 100 million citizens.

Example
Bad - 5 countries out of about 200 total nations is too small a sample. Also, the examples are cherry-picked, and so they're unrepresentative.

3. In a recent study, 100% of those who took a new birth control pill didn’t get pregnant. Only males participated in the study. Thus, the birth control pill must be very effective.

Cause
Bad - A better explanation of the correlation between taking the pill and not getting pregnant is that males don't get pregnant.

4. Oasis sounds just like The Beatles. We all know that The Beatles were one of the most influential rock bands ever. So Oasis must be one of the most influential bands, too.

Analogy
Bad - A similar sound isn't a relevant enough similarity regarding whether a band is influential.

5. Abortion is morally acceptable because renowned linguist Noam Chomsky has defended the practice of abortion, and he’s pretty smart.

Authority
Bad - Chomsky's expertise (linguistics) isn't relevant to the topic of abortion.
(Chomsky explains his view on abortion in the video to the right.)

6. Most people say the money it costs to go to law school is worth it, because lawyers earn a lot of money. So, since doctors also earn a lot, med school costs must be worth it, too.

Analogy
Pretty Good - The similarity (average money earned per profession) is relevant to whether med school is financially worth it. Assuming one thinks a large up-front investment is worth an even larger salary in the future, this arg is good.

7. My friend knows me better than anyone else, and he says I’m a decent guy. Therefore, I must be a decent guy.

Authority
Bad - Yes, my friend is a relevant expert, but he's likely to be biased in favor of me since he is my friend.

8. My sis usually keeps her car windows rolled down, though she always rolls them up right before it rains. Her car must be magical, then: rolling up her windows causes it to rain.

Cause
Bad - This is reversed! The rain probably causes her to roll up her window, not the other way around.

9. I expect this new pair of cheap, black shoes to last me about 9 months, since the last pair of cheap, black shoes I bought wound up lasting about 9 months until I wore them out.

Analogy
Pretty Good - More information would be better--for instance, it's not clear whether the two pairs of shoes are the same brand and model--but the similarities (same owner, cheapness) are relevant to the conclusion of how long the shoes will last.

10. In 2006, Philadelphia had the highest murder rate in its history. That same year, Mark Wahlberg spent a lot of time in Philadelphia while filming the movie Invincible. Thus, Mark Wahlberg’s presence in Philly probably led to such a high murder rate.

Cause
Bad - This is most likely a coincidental correlation between Wahlberg's stay in town and the high murder rate.

Penguin Digestion Experts? You Bet!

So you didn't believe me when I said that there are experts on the subject of penguin digestion? Oh, you did? Fine, well, I'll prove it to you, anyway. Here are some academic articles on the topic:

• Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating king penguins from a 2004 issue of Journal of Experimental Biology
  
• Feeding Behavior of Free-Ranging King Penguins (Aptenodytes Patagonicus) from a 1994 issue of Ecology

Of course, no list would be complete without the often-cited, groundbreaking 1985 Ornis Scandinavica article:

• Differential Digestion of Fish and Squid in Jackass Penguins Spheniscus demersus

Perhaps my favorite, though, is the following:

• Pressures produced when penguins pooh—calculations on avian defaecation from a 2003 issue of Polar Biology
  

If any of these articles are above your head (I think they're all above mine!), you might like this, uh, simpler video demonstration of penguin digestion.

Here's yet another stick-figure comic (for those keeping track, that's four total on the blog so far). This one's about correlation.

Our Inductive Minds

 Here are some more thoughtful links on inductive reasoning (or arguments by example).

• What are the benefits and dangers of generalizations?
• What makes stereotyping illogical?
• Beware: we often make snap judgments before thinking through things. Then when we do think through things, we just wind up rationalizing our snap judgments.

Arguments by Example

Here are a few dumb things about arguments by example (also called inductive arguments, talked about in the book chapter titled "Generalizations"). First, a video of comedian Lewis Black describing his failure to learn from experience every year around Halloween:


Next, this stick figure comic offers a pretty bad argument. Why is it bad? (Let us know in the comments!)